Indented, hierarchical lists aren’t the only way to outline ideas, but they’re a particularly good one. You can use any kind of well-organized writing to keep track of your project, but try to get down a comprehensive list of everything you need to include in your designs. Outlines of all shapes and sizes can help you sort out complex topics at any stage of designing your app.
Starting with a mental sweep gets all your ideas onto the page. Constructing an initial requirements outline sets you up to attack all the design challenges your project presents. Reducing problems and outlining questions strengthen your requirements outline.